PrinceWilliam informed his father, Prince Charles, grandmother Queen Elizabeth and brother Prince Harry about his son's birth shortly before an official announcement was made to the public via the press release.

From British Prime Minister David Cameron to the US President Barack Obama, congratulations have poured in for the royal couple and the new prince from all around the world.

David Cameron said: "It is wonderful news from St. Mary's, Paddington, and I am sure that right across the country, and indeed right across the Commonwealth, people will be celebrating and wishing the royal couple well.

"It is an important moment in the life of our nation but, I suppose, above all it is a wonderful moment for a warm and loving couple who have got a brand new baby boy."

Obama also released a statement on behalf of himself and wife Michelle Obama.

"Michelle and I are so pleased to congratulate The Duke and Duchess of Cambridge on the joyous occasion of the birth of their first child. We wish them all the happiness and blessings parenthood brings," he said.